NEW YORK, NY (REUTERS).- A locket-size self-portrait by Mexican artist Frida Kahlo and a historical sweep of works by Fernando Botero will be sold next month at Sotheby's auction of Latin American Masterpieces.

Sotheby's said "Autorretrato en Miniatura," or self-portrait in miniature, which sold for $225,750 in 2000, could fetch up to $1.2 million.

It is Kahlo's smallest work, measuring just 2 inches by 1-5/8 inches, the auction house said. In the oval portrait, she appears youthful and serene and wears chandelier-like earrings that emit a muted sparkle.

"This is one of the sexiest Kahlos I've ever seen. She is sending it to her lover, so she is presenting her best face forward," said Sotheby's Latin American head Carmen Melian.

"Instead of looking straight on to you as she does in a lot of paintings, she looks to the side," Melian added. "In some of the other (paintings with) sideways glances her eyes are kind of dead but here these are coquettish."

Kahlo portrays herself as glamorous, unlike other better-known works showing her in tears or spilling blood, an allusion to lifelong suffering from a teenage accident which broke her spine and pelvis.

Using a pseudonym, Kahlo signed the portrait with love to Jose Bartoli, a Catalan artist with whom she began an affair in the mid-1940s. The affair continued for years before her death in 1954 at age 47.

Sotheby's said the auction record for a Kahlo work is $5.61 million for "Roots," an oil on metal sold at Sotheby's in May 2005.

Last May, another small Kahlo work, "Survivor" fetched $1.1 million against a pre-sale estimate of $100,000-150,000 at Christie's.

The auction in New York on May 25 will also feature three decades of paintings and sculptures by Colombian artist Botero, who is known for his corpulent, rotund figures.

"It is a historical homage," said Melian. "A lot of these works are chosen because of his quintessential themes, the family groups, man on a horse, reclining nude."

"Man on a Horse," an 8-foot tall (2.4 meter) bronze sculpture, could sell for as much as $1.2 million and a painting called "A Family," has a high estimate of $1.5 million.

Another 1975 painting, "El Presidente," mocks the image of the traditional Latin American independence hero.

"He is slightly bloated," Melian said. "What everybody forgets is that Botero came to be well known for his political work in the 60s and 70s."

She added that "Pedro on a Horse," a 1977 sculpture of resin, epoxy and synthetic hair, also has political overtones and makes fun of the dictator. The horse is on red wheels, a toy-like touch, which Melian said refers to a son of Botero who died as a boy in a car accident.

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